Disk-based storage devices such as hard disk drives are used to provide non-volatile data storage in a wide variety of different types of data processing systems. A typical hard disk drive comprises a spindle that holds one or more flat circular storage disks, also referred to as platters. Each storage disk comprises a substrate made from a non-magnetic material, such as aluminum or glass, which is coated with one or more thin layers of magnetic material. In operation, data is read from and written to tracks of the storage disk via a read/write head that is moved precisely across the disk surface by a positioning arm as the disk spins at high speed. In order to control and adjust the clearance between the read/write head and the surface of the storage disk, fly height control circuitry is implemented in or otherwise supported by preamplifier circuitry of the hard disk drive device.
In a conventional fly height control framework, a resistive heating element on a slider element is incorporated near an electromagnetic pole tip of the read/write head, and fly height control circuitry is employed to apply power to the heater element sitting on the slider to adjust the fly height of the read/write head such that the spacing between the read/write head and the surface of the storage disk can be electronically controlled via thermal expansion of the electromagnet poles. As the operating temperature of the hard disk drive changes, it is desirable to keep the fly height, or spacing between the read/write head and the storage disk surface as constant as possible to achieve accurate writing and reading of data to and from the storage disk. As the clearance between read/write heads and the media surface continues to decrease, high precision fly height control circuits are required for accurate and precision fly height control, whereby electromagnetic coupling between fly height control heater element and read/write heads should be eliminated to guarantee optimal read/write performance.